the economic reasons are just bullshit, 'cause you can fix all that without getting married, it just takes alot more time. You don't need to prove to other people that you love eachother, then why do you want that piece of paper? To somepeople ( religious, and others ) it's important, 'cause it's tradition and stuff. I can understand that. But besides that, there's no reason to get married, unless you feel like you need some sort of safety, a guarantee that the your wife/husband will not leave just like that.
To marry... ah, well, it's about those two people who marry. Do like they did in Natrual Born Killers When they're on the bridge. That's one of the most romantic movies I've ever seen.
Some times nothin' is a real cool hand.